Stroke is the third leading cause of death and disability in the United States. Understanding the molecular mechanisms that lead to neuronal injury and cell death may lead to novel therapeutics to treat this devastating disorder. A variety of indices in models of ischemia indicate the involvement of oxygen free radicals, oxidative stress and DNA damage and a potential pivotal role for Poly (ADP-ribose) polymerase-1 (PARP-1) in the pathogenesis of stroke. PARP-1 is a ubiquitous and unique protein which is activated by DNA strand nicks and breaks, which can be induced by neuronal injury. Activation of PARP-1 may lead to the loss of cellular NAD+ and ATP, and the mitochondrial release and translocation of apoptosis inducing factor (AIF) resulting in acute cell injury and death. These events may be crucial in both short- and longer-term deleterious effects of stroke. However, it is unclear how PARP-1 activation leads to AIF release. Is it the NAD+ and ATP loss that accompanies PARP-1 activation that leads to AIF release and cell death or does poly(ADP-ribosyl)ation signal the release of AIF and induce the cell death cascade? Accordingly, this project is designed to explore the molecular mechanisms and consequences of PARP-1 activation following excitotoxic neuronal injury, as well as, the molecular consequences of poly (ADP-ribosyl)ation. In Specific Aim #1 we will evaluate the mechanism by which PARP-1 activation leads to release of AIF from the mitochondria and its translocation to the nucleus following cellular injury. In Specific Aim #2 we will identify PAR polymer binding proteins and investigate their role in cell death induced by PARP-1 activation. In Specific Aim #3 we will determine the role of poly (ADP-ribose) glycohydrolase (PARG) in PARP-1 mediated cell death following reactive oxygen species induced cellular injury and excitotoxic mediated neuronal injury through RNAi approaches and in PARG knockouts. And in Specific Aim #4 we will evaluate the role of overexpression of PARG in PARP-1 mediated cell death following reactive oxygen species induced cellular injury and excitotoxic mediated neuronal. Clarifying and understanding the molecular consequence of PARP-1 activation and the role poly(ADP-ribosyl)ation in the release of AIF and cell death following excitotoxic neuronal injury may yield important insight into the function of PARP-1, poly(ADP-ribosyl)ation, PARG and AIF that may identify novel targets for therapy aimed at preserving neurologic function following excitotoxic neuronal injury and stroke.